Hmmm, unable to recreate the issue after multiple "replica" tests. Might've just f'd up the export or decompile settings on the original set of runs

I was not importing via QC on that test, just an SMD reload animation.

I'll show all the steps I take from decompile to the view at the end

Originally posted by xDShot™:

You could add SWEP.ViewModelFlip = true into your lua code so it is mirrored without messing with model.

I am trying to keep everything clientside as I want it to be applyable to all servers

After several weird attempts at editing a CSS skin to work with GMOD TTT and not be Left Handed, I had to try something. Import, and then immediately export the file I was working on.

Original
2 "L_Armdummy" -1
2 -12.232234 -9.187566 -5.015311 -2.625222 -0.412431 2.958107

All I did was import and then export. Playing with the options, including the legacy rotation option, didn't keep it from looking like this afterwards

5 "L_Armdummy" -1
5 12.232234 -9.187566 -5.015312 -2.625222 -0.412431 0.183486

NOTE: The first parameter in the original is negative while the exported version is not, and the last value is shifted substantially as well. Did the same with the right arm dummy as well as some other miscellaneous bones.

21 "R_Armdummy" -1
21 11.209009 11.801211 -0.091833 1.164675 0.000000 -3.141722

24 "R_Armdummy" -1
24 -11.209009 11.801211 -0.091832 1.164675 -0.000000 0.000129

Blender ver 2.79
BST ver 2.9.1